The present invention relates to a sheet finisher having functions to take successively in a sheet finisher the sheets ejected out of an image forming apparatus such as an electrophotographic copying machine, a printer and a facsimile machine after image forming, and to conduct finishing actions such as stapling and folding for the sheets and to eject to the sheet ejecting section.
As an apparatus to collate a plurality of recording sheets each having thereon a recorded image ejected out of an image forming apparatus and to staple them with a stapler for each number of copies, a sheet finisher called a finisher is used.
The finisher is connected to an image forming apparatus main body such as a copying machine or a printer in terms of functions, and is driven to operate, interlocking with a sequence of operations of copying or printing process.
Therefore, the image forming apparatus capable of conducting image forming process at high speed requires a finisher capable of conducting high speed processing which can fulfill its functions, conforming to the processing speed of the image forming apparatus.
Finishers like that explained above are already disclosed in Japanese TOKKAISHO Nos. 60-142359, 60-158463, 62-239169, 62-288002, 63-267667, Japanese TOKKAIHEI Nos. 2-276691, 8-319054, and Japanese TOKKOHEI No. 5-41991.
A bookbinding apparatus disclosed in Japanese TOKKAISHO No. 60-183459 is one wherein a cover supplying device is provided, and bookbinding finishing work such as punching or stapling is carried out after copy sheets and a cover are superposed.
Disclosed in Japanese TOKKAIHEI Nos. 6-72064, 7-187479 and 8-192951 represents a sheet finisher having a function of midway stapling.
(1) In the means to fold a bundle of sheets which is composed of a pair of folding rollers which fold a bundle of sheets in two by pressing the central portion of the bundle of sheets in the direction of the conveyance thereof and of a means to protrude a bundle of sheets which protrudes a creased portion of the bundle of sheets while moving toward the pressure contact position of the folding rollers, a bundle of sheets has been folded in two by the method wherein the tip portion of a protruding plate of a sheet bundle protruding means is advanced to the nipping position of rotating paired folding rollers so that a portion to be creased of a bundle of sheets is protruded to be nipped for double folding.
However, when feeding a portion to be creased of a bundle of sheets toward the nipping position of the rotating paired folding rollers, a sheet on the outermost layer of the bundle of sheets is brought into contact with an outer circumferential surface of the rotating folding roller, and then is dragged in by frictional force to be deviated relatively from a sheet in an inner layer, resulting in occurrence of sheet damage such as creases or a tear.
In particular, when one or both of folding rollers are made to be an elastic roller, frictional force between an outer circumferential surface of each roller and an outermost layer of the bundle of sheets is great, and sheet damage is frequently caused.
(2) Even in the course of feeding a portion to be creased of a bundle of sheets to the nipping position of the rotating paired folding rollers, an outermost layer is damaged by friction caused by relative movement between the outermost layer in the vicinity of the tip portion of the bundle of sheets which is moved by the advancement of the tip portion of a protruding plate of a bundle of sheets protruding means and an outer circumferential surface of the rotating folding roller.
When a protruding plate is retreated after the portion near the tip portion of a bundle of sheets passes the nipping position of the rotating paired folding rollers, the bundle of sheets is sometimes withdrawn by frictional force the bundle of sheets nipped between folding rollers and the protruding plate.
(3) When both of the paired pressing rollers are metal or hard rollers, a sliding noise is generated when these rollers rotate. Further, a noise collision between both pressing rollers is generated after the trailing end portion of the bundle of sheets has passed the nipping position of the pressing rollers.
(4) Each of the conventional paired folding rollers and paired pressing rollers is a combination of a driving roller and a driven roller, and a bundle of sheets is nipped between both rollers to be conveyed. When conveying a bundle of sheets, a driving roller is away from a driven roller, and the driven roller has no conveyance driving force because it is rotated through movement of a bundle of sheets, and conveyance straightness for a bundle of sheets can not be assured. When conveying a thick bundle of sheets, in particular, improper conveyance tends to be caused.
(5) A bundle of sheets folded in two by the paired folding rollers and a sheet bundle protruding means is ejected out after the crease portion of the bundle of sheets is formed surely by paired pressing rollers. The bundle of sheets passing through the folding rollers and pressing rollers has been guided by a guide means in the past.
However, a clearance between both rollers of the paired folding rollers and that between both rollers of the paired pressing rollers are variable depending on a thickness of the bundle of sheets which passes through the rollers while being nipped between them. In the conventional guide means, it is impossible to regulate a conveyance path in the upward direction between folding rollers and between pressing rollers to comply with variable thickness of a bundle of sheets. Therefore, the bundle of sheets is not guided in the pressing rollers properly, which results in a fear of occurrence of improper conveyance.
(6) A protruding plate of the aforesaid sheet bundle protruding means has been driven so that it may move linearly in the direction perpendicular to the conveyance direction for a bundle of sheets. However, a complicated mechanism is needed for the protruding plate which is longer than the crease portion of the bundle of sheets to move linearly in a smooth manner.
The invention has been achieved to solve the problems stated above in the folding processing, and thereby to provide sheet finishers having the following structures.
(1) A sheet finisher having therein a sheet stacking section on which sheets are stacked, paired folding rollers which presses and conveys the sheets, a roller driving device which makes the paired folding rollers to be driven to convey, a protruding member which is protruded toward a pressure contact section of the folding rollers for folding double the sheets stacked on the sheet stacking section, and a protruding member driving device for protruding the protruding member toward the pressure contact section, wherein when the protruding member driving device protrudes the protruding member toward the pressure contact section, the roller driving device is suspended to drive the paired folding rollers to be conveyed.
(2) A sheet finisher having therein a sheet stacking section on which sheets are stacked, paired folding rollers which presses and conveys the sheets, a roller driving device for driving the paired folding rollers, a displacement mechanism which displaces each of the paired folding rollers in accordance with a thickness of a sheet, a protruding member which is protruded toward a pressure contact section of the folding rollers for folding double the sheets stacked on the sheet stacking section, a protruding member driving device for protruding the protruding member toward the pressure contact section, and a stopping member which stops each of the paired folding rollers so that the pressure contact section may be returned to the prescribed position for the protruding plate when each of the paired folding rollers is returned to its original position after being displaced.
(3) A sheet finisher having therein a sheet stacking section on which sheets are stacked, paired folding rollers which presses and conveys the sheets, a roller driving device which makes the paired folding rollers to be driven to convey, a displacement mechanism which displaces each of the paired folding rollers in accordance with a thickness of the sheets, a protruding member which is protruded toward a pressure contact section of the folding rollers for folding double the sheets stacked on the sheet stacking section, a protruding member driving device for protruding the protruding member toward the pressure contact section, and a stopping member which stops each of the paired folding rollers so that the pressure contact section may be returned to the prescribed position for the protruding member when each of the paired folding rollers is returned to its original position after being displaced, wherein when the protruding member driving device drives the protruding member toward the pressure contact section, the roller driving device is suspended to drive the paired folding rollers to be conveyed.
Further, preferable structures are as follows.
(Structure 1) A sheet finisher having therein a first sheet stacking section capable of stacking plural sheets, a stapling means which staples sheets stacked on the first sheet stacking section, a second sheet stacking means which is provided at the downstream side of the first sheet stacking section in the sheet conveyance direction and stacks plural sheets subjected to the stapling processing, and a sheet bundle folding means which double-folds sheets stacked on the second sheet stacking means at the central portion in the sheet conveyance direction, wherein the sheet bundle folding means is composed of at least a pair of folding rollers which press the central portion of the sheet bundle in the conveyance direction and fold the sheet bundle in two and of a sheet bundle protruding means which protrudes a portion to be folded on the sheet bundle while moving toward the pressure contact position of the folding rollers, the sheet bundle protruding means is provided with a protruding plate which comes in contact with the portion to be folded on the sheet bundle and protrudes it and with a driving means which drives the protruding plate, the tip portion of the protruding plate which comes in contact with the portion to be folded of the sheet bundle is moved by the driving means to the utmost insertion position which passes through the pressure contact position of the folding rollers to push in the portion to be folded of the sheet bundle, and the folding rollers keeps its non-rotation state until the tip portion of the protruding plate arrives at the utmost insertion position, and starts its rotation when the tip portion of the protruding plate arrives at the utmost insertion position.
(Structure 2) A sheet finisher having therein a first sheet stacking section capable of stacking plural sheets, a stapling means which staples sheets stacked on the first sheet stacking section, a second sheet stacking means which is provided at the downstream side of the first sheet stacking section in the sheet conveyance direction and stacks plural sheets subjected to the stapling processing, and a sheet bundle folding means which double-folds sheets stacked on the second sheet stacking means at the central portion in the sheet conveyance direction, wherein the sheet bundle folding means is composed of a pair of folding rollers which press the central portion of the sheet bundle in the conveyance direction and fold the sheet bundle in two and of a sheet bundle protruding means having a protruding plate which protrudes a portion to be folded on the sheet bundle while moving toward the pressure contact position of the folding rollers, and the paired folding rollers are supported to be capable of rotating in a way that the rollers are brought into pressure contact with each other by the urging means and are stopped by a stopping member arranged at the fixed position so that they may be close to each other or they may be brought into light contact with each other at the insertion position of the protruding plate.
(Structure 3) A sheet finisher having therein a first sheet stacking section capable of stacking plural sheets, a stapling means which staples sheets stacked on the first sheet stacking section, a second sheet stacking means which is provided at the downstream side of the first sheet stacking section in the sheet conveyance direction and stacks plural sheets subjected to the stapling processing, and a sheet bundle folding means which double-folds sheets stacked on the second sheet stacking means at the central portion in the sheet conveyance direction, wherein the sheet bundle folding means is composed of at least a pair of folding rollers which press the central portion of the sheet bundle in the conveyance direction and fold the sheet bundle in two and of a sheet bundle protruding means having a protruding plate which protrudes a portion to be folded on the sheet bundle while moving toward the pressure contact position of the folding rollers, a one-way clutch is provided on the drive transmission section which rotates the folding rollers, and the folding rollers are driven to rotate by the sheet bundle when the portion to be folded on the sheet bundle is protruded by the protruding plate to pass through the pressure contact position of the folding rollers while being brought into pressure contact.
(Structure 4) A sheet finisher having therein a first sheet stacking section capable of stacking plural sheets, a stapling means which staples sheets stacked on the first sheet stacking section, a second sheet stacking means which is provided at the downstream side of the first sheet stacking section in the sheet conveyance direction and stacks plural sheets subjected to the stapling processing, and a sheet bundle folding means which double-folds sheets stacked on the second sheet stacking means at the central portion in the sheet conveyance direction, wherein the sheet bundle folding means is composed of a pair of folding rollers which press the central portion of the sheet bundle in the conveyance direction and fold the sheet bundle in two, a sheet bundle protruding means which protrudes a portion to be folded on the sheet bundle while moving toward the pressure contact position of the folding rollers and of a pair of pressing rollers which are provided at the downstream side of the folding rollers in the sheet conveyance direction and press and convey the crease portion of the double-folded sheet bundle, the pressing rollers include a first roller whose surface is made of hard material and a second roller whose surface is made of elastic material, and aforesaid both rollers are brought into pressure contact with each other by an urging means.
(Structure 5) A sheet finisher having therein a first sheet stacking section capable of stacking plural sheets, a stapling means which staples sheets stacked on the first sheet stacking section, a second sheet stacking means which is provided at the downstream side of the first sheet stacking section in the sheet conveyance direction and stacks plural sheets subjected to the stapling processing, and a sheet bundle folding means which double-folds sheets stacked on the second sheet stacking means at the central portion in the sheet conveyance direction, wherein the sheet bundle folding means is composed of a pair of folding rollers which press the central portion of the sheet bundle in the conveyance direction and fold the sheet bundle in two, a sheet bundle protruding means which protrudes a portion to be folded on the sheet bundle while moving toward the pressure contact position of the folding rollers and of a pair of pressing rollers which are provided at the downstream side of the folding rollers in the sheet conveyance direction and press and convey the crease portion of the double-folded sheet bundle, and two rollers constituting the paired folding rollers and two rollers constituting the paired pressing rollers can be rotated by the driving force from the driving source.
(Structure 6) A sheet finisher having therein a first sheet stacking section capable of stacking plural sheets, a stapling means which staples sheets stacked on the first sheet stacking section, a second sheet stacking means which is provided at the downstream side of the first sheet stacking section in the sheet conveyance direction and stacks plural sheets subjected to the stapling processing, and a sheet bundle folding means which double-folds sheets stacked on the second sheet stacking means at the central portion in the sheet conveyance direction, wherein the sheet bundle folding means is composed of a pair of folding rollers which press the central portion of the sheet bundle in the conveyance direction and fold the sheet bundle in two, a sheet bundle protruding means which protrudes a portion to be folded on the sheet bundle while moving toward the pressure contact position of the folding rollers and of a pair of pressing rollers which are provided at the downstream side of the folding rollers in the sheet conveyance direction and press and convey the crease portion of the double-folded sheet bundle, and a first flat belt which is trained about a first roller constituting the paired folding rollers and a first roller constituting the paired pressing rollers and can be rotated, a second flat belt which is trained about a second roller constituting the paired folding rollers and a second roller constituting the paired pressing rollers and can be rotated, and an urging means which makes the first belt and the second belt to be in pressure contact with each other are provided, and the sheet bundle is nipped between the first flat belt and the second flat belt on a pressure contact basis to be conveyed.
(Structure 7) A sheet finisher having therein a first sheet stacking section capable of stacking plural sheets, a stapling means which staples sheets stacked on the first sheet stacking section, a second sheet stacking means which is provided at the downstream side of the first sheet stacking section in the sheet conveyance direction and stacks plural sheets subjected to the stapling processing, and a sheet bundle folding means which double-folds sheets stacked on the second sheet stacking means at the central portion in the sheet conveyance direction, wherein the sheet bundle folding means is composed of at least a pair of folding rollers which press the central portion of the sheet bundle in the conveyance direction and fold the sheet bundle in two and a sheet bundle protruding means which protrudes a portion to be folded on the sheet bundle while moving toward the pressure contact position of the folding rollers, the sheet bundle protruding means is equipped with a protruding plate which comes in contact with the portion to be folded of the sheet bundle to push it out and with a driving means to drive the protruding plate, and the protruding plate has a fulcrum for rotation at its one end in the direction perpendicular to the sheet conveyance direction, and is rotated by the driving means to protrude the portion to be folded of the sheet bundle to the pressure contact position of the folding roller.
(Structure 8)
An image forming apparatus equipped with the sheet finisher described in either one of the aforesaid Structures 1-7 above.